Molecular adsorption of NO on PdO(101)

SURFACE SCIENCE

卷:640

Article

Choi, Juhee¹  Pan, Li²  Zhang, Feng¹  Diulus, John T.¹  Asthagiri, Aravind²  Weaver, Jason F.¹ 

[1] Univ Florida, Dept Chem Engn, Gainesville, FL 32611 USA

[2] Ohio State Univ, William G Lowrie Chem & Biomol Engn, Columbus, OH 43210 USA

关键词: PdO(101);    Palladium oxide;    Density functional theory;    Nitric oxide;    Adsorption;    RAIRS;   

DOI  :  10.1016/j.susc.2015.01.010

来源: Elsevier

【 摘 要 】

We investigated the adsorption of NO on the PdO(101) surface using temperature programmed desorption (TPD), reflection absorption infrared spectroscopy (RAIRS) and density functional theory (DFT) calculations. From TPD, we find that NO reaches a saturation coverage of similar to 0.54 monolayer (ML) on PdO(101) at 90 K, and that desorption from the saturated layer produces a complex TPD trace with five pronounced maxima between 100 and 550 K. We observe negligible quantities of desorbing products other than NO during TPD, indicating that NO does not react on PdO(101) under the conditions studied. For low coverages, RAIR spectra reveal that NO adsorption at 90 K produces both flat-lying and atop configurations of NO on the coordinatively unsaturated (cus) Pd atoms of PdO(101), but that these configurations are meta-stable and transform to bridge-NO species at higher temperature. RAIRS measurements further show that NO binding on atop-Pd-cus sites becomes preferred with increasing coverage above similar to 25% of the Pd-cus density, and provide evidence of a weakly-bound state at coverages above 100% (035 ML). Consistent with our experimental findings, DFT predicts that NO preferentially adsorbs on bridge-Pd-cus sites at low coverage and that the site preference changes to atop-Pd-cus sites with increasing NO coverage, resulting in mixtures of atop-bridge NO configurations as well as an all-atop configuration. DFT also predicts that NO can adopt a flat-lying configuration on the Pd-cus row at low coverage, and can also achieve stable bonding on the fourfold Pd sites of PdO(101) at high NO coverages. Both the computational and experimental results show that NO binds on PdO(101) in multiple, local configurations even at low coverage. (C) 2015 Elsevier B.V. All rights reserved.

【 授权许可】

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